Field of the Invention
The invention relates to a pressure sensor catheter. This type of catheter is used for measuring pressures inside a body lumen.
Description of Related Art
These measurements can for example be used to calculate the fractional flow reserve (FFR). FFR provides a measure of the degree to which a stenosis obstructs the fluid flow in the body lumen, for example in a blood vessel. FFR is calculated on the basis of the pressure on the proximal side of the stenosis and the pressure on the distal side of the stenosis, typically at maximum vasodilation. For example, the pressures upstream and downstream of the stenosis are measured. The FFR ratio is defined as the downstream pressure divided by the upstream pressure. If the FFR ratio is low, a physician can decide to take appropriate actions, such as placing a stent. Typically, an FFR ratio below 0.75 is indicative of a stenosis which requires intervention.
In conventional pressure sensor catheters at least one pressure sensor has to be moved to the distal side of the stenosis to measure the pressure locally.
For example, in one type of conventional device, a sensor is mounted on the tip of a guidewire.
Moving the sensor through a stenosis requires a sensor which is as small as possible. Another reason for using a small sensor is to minimize the influence of the catheter on the blood flow and hence the measured pressure. To keep the sensor small in conventional devices, various compromises have been made in the design thereof. For example, the sensors are half-bridge sensors and/or do not comprise outside pressure equalization, both leading to less accurate measurements. In addition, mounting such a small sensor in a way that makes it insensitive to bending is complicated.
A goal of the invention is to overcome the above problems and to provide a pressure sensor catheter which can be introduced in a body lumen to accurately measure the pressure on the distal side of a flow restriction, such as a stenosis, even for narrow passages.